Abstract:
Nitrogen (N) is one of the essential macronutrients for rice growth and yield. Most of the nitrogen in the soil is in organic form and nitrogen release depends on organic fertilizers type. The element of material or organic fertilizer different affect to nitrogen content and nitrogen mineralization time. The objective of this research was to determine the effect of different types of organic fertilizers on the availability of nitrogen in organic paddy soil and non-organic paddy soil and determine the suitability of application different types of organic fertilizers timing on growth and yield of rice. This study divided into 2 experiments, experiment 1: effect of organic fertilizer
types on change of nitrogen forms from organic fertilizers in a flooded condition. The experimental design was 2x4 factorial in completely randomized with 3 replications. Factor in the experiment has 2 factors. The first factor was paddy soil 2 type with organic paddy soil and non-organic paddy soil. The second factor was three types of organic fertilizers with cow manure, compost, sunn hemp,
and no organic fertilizers. Eight treatments were used consisting of 1. non-fertilizer application in organic paddy soil (CN-O), 2. amended with cow manure in organic paddy soil (CM-O), 3. amended with compost in organic paddy soil (CP-O), 4. amended with green manure as sunn hemp in organic paddy soil (SH-O), 5. non-fertilizer application in non-organic paddy soil (CN), 6. amended with cow manure in non-organic paddy soil (CM), 7. amended with compost in non-organic paddy soil (CP) and 8. amended with green manure as sunn hemp in non-organic paddy soil (SH). Each organic fertilizer was amended at a rate of 300 mg N/kg. Calculate the nitrogen content of total nitrogen of three organic fertilizer. The result shows that CP-O has pH in soil highest (7.2) and that was neutral. While SH has pH in a solution of soil highest (7.6) and that was slightly alkaline and end of incubation of all treatment were neutral. The pH in soil on non-organic and organic paddy soil was neutral after flooding 14 days due to reduction reaction. While CM was the highest electrical conductivity (0.37 mS/cm) and this did not affect plant growth and the highest hydrolyzable nitrogen of soil (412.04 mg N/kg) and significant with SH, CM-O, SH-O, CP-O, and CN-O, respectively. SH was the highest cumulative nitrogen mineralization in soil (349.35 mg N/kg) and significant differences with all treatment. Three organic fertilizers in organic paddy soil were the higher cumulative nitrogen mineralization in soil than non-organic paddy soil. The predicted nitrogen mineralization of organic paddy soil was SH-O highest mineralization potential (N0) as 114.53 mg N/kg and following by CM-O CP-O and CN-O, respectively (109.90 107.23 and 95.34 mg N/kg, respectively). In addition, mineralization rate (k) of all treatment was not significant as around 0.1992 to 0.2095. The predicted nitrogen mineralization of non-organic paddy soil was SH highest mineralization potential as 314.10 mg N/kg and significant with CM and CN, respectively. The mineralization rate of three organic fertilizer was non-significant around 0.2302 to 0.3464. Experiment 2: effect of organic fertilizer and organic fertilizer application timing were investigated. This experiment was organic rice soil in a pot and using randomized complete block design (RCBD) with 4 replications. Seven treatments consisted of 1. no fertilizer application (Control), 2. compost application 100% of nitrogen requirement at transplanting (Compost1), 3. split compost application 50% of nitrogen requirement at transplanting and maximum tillering stage (Compost2), 4. cow manure application 100% of nitrogen requirement at transplanting (Cow manure1), 5. split cow manure application 50% of nitrogen requirement at transplanting and maximum tillering stage (Cow manure2), 6. split compost application 50% of nitrogen requirement at transplanting and cow manure application at maximum tillering stage (Com1+Cow1) and 7. split compost application 50% of nitrogen requirement at transplanting and cow manure application 25% at maximum tillering stage and panicle initiation stage. Nitrogen requirement for rice was to 12 kg N/rai. Organic fertilizers rate was calculated based on soil nitrogen content before transplanting and organic fertilizers mineralization which calculated from the equation from experiment 1. The experiment was planting for two rice crops. The result from the first crop shows that all treatment was not significant but tended to Com1+Cow1 was the highest height of rice (141.88 cm). While, Com1+Cow2 was highest in tiller number (60.50 tiller/pot) and significant with all treatment except Cow manure1 and Compost2 (57.00 and 53.00 tiller/pot, respectively). All treatments were not affected to panicle number and grain dry weight at 14% moisture. It tends to Com1+Cow2 was highest panicle number (72.00 panicles/pot) and grain dry weight at 14% moisture (27.73 g/pot). Total nitrogen uptake in control was highest total nitrogen uptake (1.78 g/pot) as a result of nutrient dilution effect. Soil and solution pH shows that all treatment was not significant and equal to 6.4-6.6 that (slightly acid to neutral). Change in ammonium content show that all treatment was not significant but compost2 was highest cumulative nitrogen mineralization and hydrolyzable nitrogen in the soil (14.13 and 80.09 mg N/kg, respectively). Compost2 was the highest total nitrogen at the end of incubation (2.38 mg N/kg) and significant with Compost2 Compost1 and Cow manure2, respectively. In the second crop, the results of growth and yield show that all treatment was not significant in height but tend to Com1+Cow1 was the highest height of rice (131.48 cm) similar to the first crop. Com1+Cow1 was highest tiller number (23.25 tiller/pot) and significant with Cow manure1 and Control (20.25 and 17.25 tiller/pot). Organic fertilizers application were not significant but tend to cow manure1 has highest panicle number (20.75 panicles/pot). Compost1 was highest grain dry weight at 14% moisture (44.30 g/pot) and all treatment was not significant of 1000-grain weight. Total nitrogen uptake result shows that Com1+Cow1 was highest of total nitrogen uptake. The results of soil and solution pH show that all treatment was not significant. Change in soil ammonium showed Cow manure1 was highest soil ammonium content (12.34 mg N/kg) and significant with Compost1 and Control. Cow manure1 was the highest total nitrogen at the end of incubation (2.38 g N/kg). Hydrolyzable nitrogen in all treatments was not significant but Cow manure1 was highest (37.82 mg N/kg). Also compost application 100% of nitrogen requirement at transplanting (Compost1) enhanced grain weight and reduce the expenses of organic fertilizers application.